Various types of transportable vessels are used for packaging various commercial and industrial gases at superatmospheric pressure. One type of vessel is a gas cylinder, an example of which is an elongate metal tank adapted to contain gas at relatively high pressure. An upper axial end of the cylinder has a neck containing an opening to the interior. A shut-off valve is mounted in closure of the neck opening. Another type is a container, a vessel that may have substantially larger volume than a cylinder. A container may have several such shut-off valves each mounted in closure of a respective opening in the container wall.
A representative shut-off valve comprises a first port fitted in sealed relation to an opening in a vessel wall, a second port, and a valve mechanism that is operable via an external actuator, handle, or tool, to allow and disallow fluid communication between the two ports. The second port is externally available for connection to a gas supply source when the cylinder is to be filled and for connection to a gas utilization system at a facility that uses gas stored in the cylinder. The valve mechanism comprises a stem that is rotated by the external actuator, handle, or tool to open and close the valve. An external actuator may be either manual or powered. An electric- or pneumatic-powered prime mover is an example of a power actuator. A wrench is an example of a hand tool for turning the valve stem.
The representative valve may be a globe style valve whose stem is rotatable more than one full turn between closed and full open positions. Opening the valve allows contained gas to pass from the vessel by entering the first port, flowing through the valve, and exiting via the second port. In such case, the first port forms a gas inlet connected to the vessel, and the second port a gas outlet. The gas outlet may be connected via a conduit to a point of use of the gas.
Such vessels can hold gases that may be considered hazardous, examples of such gases including chlorine and sulfur dioxide. A facility that utilizes one or more of such gases in a process, or processes, conducted at the facility may, for example, have any number of such vessels containing the same or different gases on the premises. When connected to a gas handling system at the facility, such vessels are able to deliver gas, or gases, into the system once their shut-off valves have been opened. Because of inherent characteristics of certain gases, vessels that contain them may be housed in locations that are remote from attending personnel, and/or the vessels may be in use at times when personnel are absent.
When a vessel, or vessels, is, or are, in use at a facility, and gas leakage is detected, it may be appropriate to shut off all vessels in an attempt to minimize further gas leakage. Accordingly, an automatic gas leak detection and valve shut-off system may be employed at a facility to address such a situation. Such a system may include a power actuator associated with the shut-off valve of each vessel. Examples of known valve closure systems include electromechanical actuators and pneumatic actuators.
Commonly owned U.S. Pat. No. 6,170,801 discloses a valve closure system that mounts on a gas-containing vessel in association with a valve having a rotatable stem that opens and closes the valve. The closure system comprises a mounting bracket and an air motor. With the valve open, the bracket is fit to the valve and a coupling on an external end of the air motor shaft is fit to the stem. The long axis of the air motor is coincident with the axis of the stem. When pressurized air is delivered to the air motor, the motor shaft rotates the stem in a sense that closes the valve. The long axis of the motor adds to the overall length of the closure system. With turning of the valve stem being in one-to-one correspondence (i.e. a 1:1 ratio) to turning of the motor shaft, the air motor must be able to deliver output torque corresponding to the torque requirement for the valve.